Large capacity solid state battery

ABSTRACT

A technique relating to a battery structure is disclosed. A base substrate and a battery layer having a support substrate are prepared. The battery layer includes a protection layer formed on the support substrate, a film battery element formed on the protection layer and an insulator covering the film battery element. The battery layer is placed onto the base substrate with the bottom of the support substrate facing up. The support substrate is then removed from the battery layer at least in part by etching while protecting the film battery element by the protection layer. A stacked battery structure including the base substrate and the two or more battery layers is also disclosed.

BACKGROUND Technical Field

The present invention, generally, relates to battery technology, andmore particularly, to a stacked battery structure and a method forfabricating thereof. The present invention also relates to a method offabricating a stacked structure.

Description of Related Art

Recently, a solid thin film battery (STFB) has attracted attention as apromising rechargeable battery for the Internet of Things (IoT) devicesin terms of its small footprint and safe nature. However, generally, aSTFB does not have enough energy capacity. Since the capacity of theSTFB is limited due to limitations on cathode thickness and thickeningof the STFB is known to be technically difficult, stacking (or3-dimensional packaging) is one of the solutions for enlarging thecapacity of the battery using the STFB. However, the thickness of thesubstrate on which the STFB is fabricated becomes a bottleneck inachieving a large capacity battery.

In the field of semiconductor device fabrication processes, waferback-grinding, which is a process for reducing wafer thickness bymechanical grinding, is known as the most common technique for waferthinning However, there are several disadvantages in applying the waferback-grinding process to fabricate a stacked film battery structure.Such disadvantages include a limit of the substrate thickness that canbe thinned by mechanical grinding. Even though the wafers can be thinneddown to 75 to 50 um, it is still several times thicker than thethickness of the STFB, which can be less than or equal to about tenmicrometers (˜10 um).

A laminated thin film battery including a first thin film battery and asecond thin film battery has been proposed, in which cathode currentcollectors and anode current collectors are formed on first surfaces,and the first and second thin film batteries are laminated in such atype that the respective first surfaces face each other (U.S. Pat. No.9,634,334). However, the thickness of the substrate on which the thinfilm battery is fabricated is still a bottleneck to achieve a largecapacity battery.

A monolithically integrated thin-film solid-state lithium battery devicethat includes multiple layers of lithium electrochemical cells has beenalso proposed (US Patent Application US2012/0058380). However, since themultiple layers of the lithium electrochemical cells are fabricatedsequentially by physical vapor deposition techniques, materials that canbe adopted for the cathode is limited in the integrated thin-filmsolid-state lithium battery device. The cathode materials such as LiCoO₂requires a high temperature annealing process that cannot be employedsince it makes sequential stacking difficult from a view point of heatresistance of other components.

Therefore, there is a need for a novel battery structure that is capableof thinning total thickness of the battery structure while maintainingits capacity.

SUMMARY

According to embodiments of the present invention, a method forfabricating a stacked battery structure is provided. The method includespreparing a base substrate. The method also includes preparing a batterylayer formed on a support substrate, in which the battery layer includesa protection layer formed on the support substrate, a film batteryelement formed on the protection layer and an insulator covering thefilm battery element. The method further includes placing the batterylayer onto the base substrate with the bottom of the support substratefacing up. The method further includes removing the support substratefrom the battery layer at least in part by etching while protecting thefilm battery element by the protection layer.

The stacked battery structure fabricated by the methods according to theembodiments of the present invention can have thinner total thicknesswhile maintaining capacity and the production cost of the stackedbattery structure, which is also low since the support substrate onwhich the film battery element is formed can be thinned, or eliminatedby etching while protecting the film battery element.

In a preferable embodiment, the method further includes alternatelyrepeating stacking an additional battery layer having another supportsubstrate with a bottom of the other support substrate facing up, andremoving the other support substrate from the additional battery layerat least in part by etching, until a desired number of the batterylayers are stacked. The additional battery layer includes a protectionlayer, a film battery element and an insulator. Thereby, capacity of thestacked battery structure can be enlarged while keeping total thicknessof the battery structure. Since the thickness to be increased bystacking one unit of the battery layer is small, it is possible toincrease the number of battery layers stacked within a certainthickness.

In other preferable embodiments, removing the support substrate includeswet-etching the support substrate until reaching the protection layer.Since the support substrate can be eliminated completely by costeffective wet-etching without damage on the film battery element behindthe protection layer, it is possible to reduce the total thickness asmuch as possible while suppressing an increase in fabrication cost dueto substrate thinning

In further preferable embodiments, the support substrate is made ofglass material, the wet-etching can include etching using a bufferedhydrofluoric acid (BHF) solution, the protection layer works as an etchstopper against the BHF solution and the base substrate is made of amaterial having resistance against the BHF solution. Thus, throughput ofthe support substrate removal can be increased and a tool or materialfor protecting the base substrate can be made unnecessary.

In further preferable embodiments, the base substrate is provided with abase battery layer formed thereon, which includes a film battery elementformed on the base substrate and an insulator covering the film batteryelement formed on the base substrate. The battery layer is placed ontothe insulator of the base battery layer in placing the battery layeronto the base substrate. This makes the fabrication process moreefficient.

In further other preferable embodiments, the film battery element ineach battery layer includes current collectors and a battery cell incontact with the current collectors. The method further includes forminga via hole in the battery layers to extend through at least one layer toa layer under the at least one layer, wherein the support substratesdown to the layer have been eliminated by the etching. The methodfurther includes filling a conductive material in the via hole ordepositing a conductive material on an inner surface of the via hole toform a conductive path electrically connected to at least one currentcollector in the battery layers. Since the via hole extending at leasttwo battery layers can be fabricated collectively, the fabricationprocess for the conductive path can be simplified.

In further other preferable embodiments, forming the via hole includesdrilling at least one protection layer and at least one insulator in thebattery layers by laser processing while leaving the current collector.Fabrication cost for the conductive path can therefore be reduced.

In further other preferable embodiments, the via hole has pluralsections and the plural sections have at least one horizontal dimensionenlarged from bottom to top in the battery layers stacked on the basesubstrate and overlap each other in a horizontal plane with respect tothe base substrate. The conductive path has contacts with plural currentcollectors in different battery layers, in which each contact isobtained at a surface of each of the plural current collectors. Thereliability of contacts between the conductive path and the currentcollectors can therefore be improved.

According to other embodiments of the present invention, a stackedbattery structure including a base substrate and two or more batterylayers on the base substrate is provided. Each battery layer includes aprotection layer; a film battery element formed on the protection layer;and an insulator covering the film battery element. In the stackedbattery structure, the battery layers are stacked in an upside downmanner with respect to the base substrate such that each insulator is ona base substrate side, each protection layer is on a side opposite tothe base substrate side and the insulator of upper one of the batterylayers bonds to a lower one of the battery layers.

The stacked battery structure according to the embodiments of thepresent invention can have thinner total thickness while maintaining itscapacity or can have large capacity while keeping total thickness of thebattery structure. Since the thickness to be increased by stacking oneunit of the battery layer is small, it is possible to increase thenumber of battery layers stacked within a certain thickness.

In other preferable embodiments, the insulator of the upper one of thebattery layers has a surface bonding to the protection layer of thelower one of the battery layers. In further other preferable embodiment,there is no rigid material interposed between the insulator of the upperone and the protection layer of the lower one. This makes it possible toreduce the total thickness.

According to further other embodiments of the present invention, anelectronic device including an electronic component and a stackedbattery structure is provided. The stacked battery structure includes abase substrate, two or more battery layers on the base substrate, and awiring layer for connecting the stacked battery structure with theelectronic component. Each battery layer includes a protection layer.Each battery layer also includes a film battery element formed on theprotection layer, which is used for supplying power to the electroniccomponent through the wiring layer. Each battery layer further includesan insulator covering the film battery element. In the electronicdevice, the battery layers are stacked in an upside down manner withrespect to the base substrate such that each insulator is on a basesubstrate side, each protection layer is on a side opposite to the basesubstrate side and the insulator of upper one of the battery layersbonds to a lower one of the battery layers.

The electronic device according to further other embodiment of thepresent invention can have a large capacity battery while keeping asmall footprint for the battery.

According to further other embodiments of the present invention, astacked battery structure is provided. The stacked battery structure isfabricated by placing a battery layer having a support substrate onto abase substrate with the bottom of the support substrate facing up, inwhich the battery layer includes a protection layer formed on thesupport substrate; a film battery element formed on the protection layerand an insulator covering the film battery element. The stacked batterystructure is fabricated by further removing the support substrate fromthe battery layer at least in part by etching while protecting the filmbattery element by the protection layer.

The stacked battery structure according to the embodiments of thepresent invention can have thinner total thickness while maintaining itscapacity since the support substrate on which the film battery elementis formed can be thinned, or eliminated while protecting the filmbattery element.

According to another embodiment of the present invention, a method forfabricating a stacked structure is provided. The method includespreparing a base substrate. The method includes preparing a deviceelement layer having a support substrate, which includes a protectionlayer formed on the support substrate, a device element formed on theprotection layer and an adhesive material covering the device element.The method includes placing the device element layer onto the basesubstrate with the bottom of the support substrate facing up. The methodfurther includes etching the support substrate from the bottom of thesupport substrate until reaching the protection layer of the deviceelement layer.

The stacked structure according to the embodiments of the presentinvention can have thinner total thickness while maintaining the numberof stacked device layers in the stacked structure since the supportsubstrate on which the devices is formed is eliminated while protectingthe device element.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings. Note that the sizes andrelative positions of elements and layers in the drawings are notnecessarily drawn to scale. Some of these elements or layers arearbitrarily enlarged and positioned for improving legibility of drawing.

FIG. 1 illustrates a cross-sectional view of a stacked battery structureaccording to an exemplary embodiment of the present invention.

FIGS. 2A, 2B, 2C, 2D and 2E illustrate cross-sectional views ofstructures being obtained at each step in a first one-third part of thefabrication process of a stacked battery structure according to anexemplary embodiment of the present invention.

FIGS. 3A, 3B and 3C illustrate cross-sectional views of structures beingobtained at each step in a middle one-third part of the fabricationprocess of the stacked battery structure according to the exemplaryembodiment of the present invention.

FIGS. 4A, 4B and 4C illustrate cross-sectional views of structures beingobtained at each step in a last one-third part of the fabricationprocess of the stacked battery structure according to the exemplaryembodiment of the present invention.

FIG. 5 shows a schematic diagram of connected current collectors in thestacked battery structure according to an exemplary embodiment of thepresent invention.

FIGS. 6A, 6B, 6C, 6D, 6E and 6F illustrate a process for fabricating avia with a stepped shape structure in accordance with exemplaryembodiments of the present invention.

FIGS. 7A and 7B illustrate cross-sectional views of stacked batterystructures according to other embodiments of the present invention.

FIGS. 8A and 8B depict electronic devices including a stacked batterystructure according to one or more exemplary embodiments of the presentinvention.

FIGS. 9A and 9B describe a comparison between stacked battery structureswith and without applying a novel support substrate removal processaccording to exemplary embodiments of the present invention.

DETAILED DESCRIPTION

Now, the present invention will be described using particularembodiments, and the embodiments described hereafter are understood tobe only referred to as examples and are not intended to limit the scopeof the present invention.

One or more embodiments according to the present invention are directedto a stacked battery structure, a method for fabricating the stackedbattery structure, a stacked battery structure fabricated by the method,an electronic device including the stacked battery structure, in which alarge battery capacity can be achieved in a volume efficient manner.

Hereinafter, with reference to FIG. 1, a stacked battery structureaccording to an exemplary embodiment of the present invention will bedescribed.

FIG. 1 illustrates a schematic of a stacked battery structure 100. Across-sectional view of the stacked battery structure 100 is shown inFIG. 1. As shown in FIG. 1, the stacked battery structure 100 includes abase substrate 102; a plurality of battery layers 110, 140 stacked onthe base substrate 102, each of which includes at least one film batteryelement; a pair of vias 172, 174 formed in the stacked battery layers110, 140; and a wiring layer 180 built on the top of the stacked batterylayers 110, 140.

In the described embodiment, the battery layers stacked on the basesubstrate 102 may include an upward base battery layer 110 with its filmbattery element facing up and two or more downward battery layers 140with its film battery element facing down. In the stacked batterystructure 100 shown in FIG. 1, there is one upward base battery layer110 and two downward battery layers 140A, 140B stacked on the upwardbase battery layer 110.

The upward base battery layer 110 may be formed on the base substrate102. The upward base battery layer 110 may include a film batteryelement 120 formed on the base substrate 102 and an insulator 132 thatcovers the film battery element 120. The downward battery layers 140 maybe disposed on the insulator 132 of the upward base battery layer 110.

Each downward battery layer 140 includes a protection layer 144, a filmbattery element 150 formed on the protection layer 144 and an insulator162 covering the film battery element 150.

Note that the orientation of the film battery element 150 in thedownward battery layer 140 is opposite to that of the upward basebattery layer 110. Each downward battery layer 140 is disposed on itsunderlying battery layer (110 or 140) in an upside-down manner withrespect to the base substrate 102 such that each insulator 162 is on theside of the base substrate 102 and each protection layer 144 is on aside opposite to the base substrate side. The downward battery layers140 are stacked such that the insulator of an upper one of the batterylayers (e.g., 162B) bonds to a lower one of the battery layers (e.g.140A), and the insulator of the lowermost downward battery layer (i.e.,162A in FIG. 1) bonds to the upward base battery layer 110.

The base substrate 102 may be made of any one of rigid materials such asa silicon, an alumina ceramic, a glass, mica, etc., to name but a few.However, since the fabrication process of the film battery element 120may include a heating process for cathode material, thus, the basesubstrate 102 is preferably made of heat-resistant materials that canwithstand the heating process for the cathode material.

The protection layer 144 may be made of a chemically resistant materialthat can be usable as an etch stopper against wet-etching, which may beperformed in the fabrication process of the stacked battery structure100. The fabrication process will be described later. In a particularembodiment, the protection layer 144 is made of a chemically inertmaterial usable as an etch stopper against wet-etching using bufferedhydrofluoric acid (BHF) solution. The protection layer 144 can alsoprevent moisture or liquid from invading components of the film batteryelement 150, such as an electrolyte. In view of the fabrication processof the film battery element 150, the protection layer 144 onto which thefilm battery element 150 is fabricated is preferably made ofheat-resistant materials that can withstand the heating process for thecathode material. In view of the fabrication process of the vias 172,174, the protection layer 144, through which via holes are fabricated,is preferably made of material having relatively lower dry etchresistance that can be laser processed. Such material includes, but isnot limited to, silicon nitrides SiN (e.g., Si₃N₄). However, in otherembodiments, other inorganic materials such as poly-silicon may also beused as long as the material does not interfere with via holefabrication and has etching and heat resistance. The material of theprotection layer 144 can be deposited by virtually any standard meansincluding vapor deposition techniques. Thickness of the protection layer144 may range from about 0.1 to about 1.0 um.

The insulators 132, 162 may be made from adhesive material such as aresin having a certain curing temperature that may be in a range of150-250 degrees Celsius, for example. Any laser-processable adhesiveresin that can be drilled by laser may be used as the material for theinsulator 132, 162. Such resin may include BCB (benzocyclobutene) resin,etc. to name but a few.

The upward base battery layer 110 and the lowermost downward batterylayers 140A may be bonded by the insulators 132, 162A of the batterylayers 110, 140A. The lower and upper downward battery layers (e.g.,140A, 140B) may be bonded by the upper insulator (e.g., 162B) that isprovided therebetween.

By curing, the insulators 132 of the upward base battery layer 110 andthe insulator 162A of the lowermost downward battery layers 140A may beintegrally fixed together. The insulator of the upper battery layer(e.g., 162B) may have a surface bonding to the protection layer of thelower battery layer (e.g., 144A). In the final stacked battery structure100 shown in FIG. 1, there is no rigid material interposed between theinsulator of the upper one (e.g., 162B) and the protection layer of thelower one (e.g., 144A).

Each film battery element 150 in the downward battery layer 140 mayinclude a cathode current collector (CCC) 152; a cathode 154 connectedto the cathode current collector 152; an electrolyte 156 having aninterface to the cathode 154; an anode 158 having an interface to theelectrolyte 156; and an anode current collector (ACC) 160 connected tothe anode 158. The cathode 154, the electrolyte 156 and the anode 158constitutes a battery cell that is in contact with the currentcollectors 152, 160. The film battery element 120 in the upward basebattery layer 110 may have a structure identical or similar to that ofthe film battery element 150 in the downward battery layer 170 and mayalso include a cathode current collector 122, an anode current collector130 and a battery cell in contact with the current collectors 122, 130,which may contain a cathode 124, an electrolyte 126 and an anode 128.

The cathode current collectors 122, 152A, 152B and the anode currentcollectors 130, 160A, 160B may be made of any one of metals (e.g., Cu,Pt, Al, Au, etc.) and other conductive materials (e.g. graphite, carbonnanotube , etc.) as long as it is adequate for respective material ofthe cathode 124, 154 and the anode 128, 158. The cathode currentcollector 122 and the anode current collector 130 may be formed on thebase substrate 102. The cathode current collectors 152A, 152B and theanode current collectors 160A, 160B may be formed on the respectiveprotection layers 144A, 144B.

Note that if the protection layer 144 is made of conductive material,there may be an additional non-conductive layer interposed between thecurrent collectors 152, 160 and the protection layer 144. Also note thatif the base substrate 102 is made of conductive material, there may bean additional non-conductive layer between the current collectors 122,130 and the base substrate 102.

The cathode 124, 154 may be made of crystalline or nano-crystallinelithium intercalation compounds such as LiCoO₂, LiMn₂O₄, to name but afew. The material of the cathode 124, 154 can be deposited by virtuallyany standard means including vapor deposition techniques such assputtering, and the film obtained by low temperature deposition may beannealed at a predetermined annealing temperature (usually in a range of500-700 degrees Celsius) to obtain fully crystalline phases.Alternatively, the material of the cathode 124, 154 can be deposited byvirtually any standard means including vapor deposition technique whileheating the substrate at a predetermined deposition temperature. Otherunannealed cathode material such as nano-crystalline Li_(x)Mn_(2-x)O₄may not be excluded from candidates for the cathode material.

The electrolyte 126, 156 may be any one of solid electrolytes such asceramic electrolyte including lithium oxide based electrolytes (e.g. alithium phosphorus oxynitride (LiPON), lithium lanthanum titanium oxide(LLTO), etc.), lithium sulfide based electrolytes and other lithiumphosphate based electrolytes such as a lithium borophosphate (LiBP). Theelectrolyte 126, 156 can be deposited by virtually any standard meansincluding vapor deposition techniques such as sputtering. In theembodiment shown in FIG. 1, the electrolyte 126, 156 may be deposited onthe cathode 124, 154 so as to fully cover surface and edges of thecathode 124, 154.

The anode 128, 158 may be made of any one of a silicon and materialsthat have a melting point higher than curing temperature of theinsulator 132, 162. Specifically, the anode 128, 158 may be Li-freeanode, in which the anode is formed by electroplating of metalliclithium or lithiation at the interface between the electrolyte 126, 156and the anode current collector 130, 160 upon the initial charge.Alternatively, the anode 130, 160 may be Li-ion anode such as silicontin oxynitride (SiTON), tin and zinc nitrides. By employingaforementioned anode material, the anode 130 can withstand temperaturesfor curing the insulator 132, 162. However, in other embodiments,metallic lithium, which has a melting point of 180 degrees Celsius, maynot be excluded from candidates for the anode material as long as theanode material can withstand the curing temperature for curing theinsulator 132, 162.

In a preferable embodiment, each film battery element 120, 150 can befabricated as an all-solid-state thin film battery, more specifically,an all-solid-state lithium ion thin film battery. In a particularembodiment, the total thickness of the film battery element 120, 150 maybe less than or equal to about ten micrometers (e.g. ˜10 um).

The vias 172, 174 may be formed within the stacked battery layers 110,140 to provide a conductive path between an external device and the filmbattery elements 120, 150 in the stacked battery layers 110, 140. Notethat in the described embodiment, the vias 172, 174 may extend throughat least one battery layer (140B, 140A in FIG. 1) to a layer under theat least one battery layer (110 in FIG. 1), which includes one or moreprotection layers (144B, 144A in FIG. 1) and one or more insulators(162B, 162A, 132 in FIG. 1).

Each via 172 (or 174) may be formed in a via hole that is opened throughat least one of the stacked battery layers 110, 140. The via hole may beformed through one or more battery layer 110, 140, collectively. The viaholes 172, 1744 are made conductive by filling conductive material(e.g., solder paste) or depositing conductive material (e.g., metal) onits inner surface to form the vias 172, 174.

Each via 172 (or 174) is electrically connected to at least one of thecurrent collectors 122, 152 (or 130, 160) in the stacked battery layers110, 140. In one or more embodiments, each via has contacts with pluralcurrent collectors in different battery layers, in which each contact isobtained at a surface of each of the plural current collectors.

In the described embodiment shown in FIG. 1, the via 172 may havecontacts at respective surfaces of the cathode current collectors (e.g.,122, 152A, 152B). The via 174 may have contacts at respective surfacesof the anode current collectors (e.g., 130, 160A, 160B).

Note that according to FIG. 1, it seems that the via 172 (or 174) is notin contact with the current collectors 152A, 152B (160A, 160B) of thedownward battery layers 140A, 140B. However, the vias 172 (or 174) arein contact with the current collectors 152A, 152B (or 160A, 160B) atdifferent cross-sections, respectively. The outlines of the currentcollectors 152, 160 at different cross sections are indicated by dashedlines in FIG. 1.

The wiring layer 180 that is built on the top of the stacked batterylayers 110, 140 may have a conductive element (wiring pattern)connecting the vias 172, 174 with external terminals, which may beconnected to the external device such as a CPU (Central ProcessingUnit), memory, etc. The wiring layer 180 may also be made from a resinas insulator for the wiring layer. The resin may be any one of a BCB(benzocyclobutene) resin, a polyimide and other polymers.

The structure of the stacked battery structure 100 may not be limited tothe specific embodiment shown in FIG. 1. Although not shown in FIG. 1,there may be an additional layer in the stacked battery structure 100.For example, the film battery element 120, 150 may be covered by otherprotective coatings before deposition of resin of the insulator 132,162.

Also, the layout of the film battery elements 120, 150 within thestacked battery structure 100 may not be limited to the specificembodiments shown in FIG. 1 where all of the film battery elements 120,150 are connected by the via 172, 174 in parallel.

In other embodiments, such a layout where at least two of the filmbattery elements 120, 150 are connected in series by using vias and/or asurface wiring layer such as the wiring layer 180 may be employed.Connecting the film battery elements 120, 150 in series can increase aterminal voltage of the stacked battery structure 100 while maintaininga small footprint of the stacked battery structure. Since electrodematerials that are not practically used so far due to their lowerpotential difference can be employed by connecting the elements inseries, a range of design choices for electrode materials can bebroadened. Also, in other aspects, a plurality of terminal voltages canbe obtained from the stacked battery structure 100 with appropriateserial connections.

In a particular embodiment, interconnections between plural layers canbe achieved by not only a via but also other surface wiring layer suchas the wiring layer 180 after routing each electrical path from eachcurrent collector to top of the stack by a respective via structure. Thevia may be opened through all layers including top to bottom layers ormay be opened through a part of the layers by terminating the hole at acurrent collector of the middle layer. Even if the via is opened throughthe all layers from top to bottom, the via may not be required toconnect with all current collectors.

Hereinafter, with reference to a series of FIGS. 2A-2E, FIGS. 3A-3C andFIGS. 4A-4C, a process for fabricating a stacked battery structure 100according to an exemplary embodiment of the present invention will bedescribed.

FIGS. 2A-2E, FIGS. 3A-3C and FIGS. 4A-4C illustrate cross-sectionalviews of structures being obtained at each step of the fabricationprocess of the stacked battery structure 100.

As shown in FIG. 2A, the fabrication process may include a step ofpreparing a base substrate 102 that has a film battery element 120fabricated thereon. In a particular embodiment, the base substrate 102prepared by this step is made of bulk silicon, which has resistanceagainst BHF solution and heat. The film battery element 120 thatincludes a cathode current collector 122, a cathode 124, an electrolyte126, a anode 128 and an anode current collector 130 may be fabricated onthe base substrate 102 by virtually any standard process as exemplarilydescribed below with respect to the film battery element 150 for thedownward battery layer 140.

As shown in FIG. 2B, the fabrication process may also include a step offorming an insulator 132 over the film battery element 120 and the basesubstrate 102 to obtain a base battery layer 110 formed on the basesubstrate 102. In a particular embodiment, this step may include asub-step of depositing an insulation material over the film batteryelement 120; and a subsequent sub-step of flattening of the insulationmaterial to obtain a flat top surface 132a by adequate method asexemplarily described below with respect to the downward battery layer140.

As shown in FIG. 2C, the fabrication process may further include a stepof preparing a support substrate 142 that has a protection layer 144formed thereon. The support substrate 142 onto which the film batteryelement 150 is fabricated is preferably made of heat-resistant materialsthat can withstand the heating process for the cathode 154. In aparticular embodiment, the support substrate 142 prepared by this stepis made of glass material, which has relatively high etch rate in theBHF solution and also heat resistance. The protection layer 144 may bemade of a chemically resistant material that can be usable as an etchstopper against wet-etching using the BHF solution. In a particularembodiment, the protection layer 144 is made of silicon nitrides SiN(e.g., Si₃N₄), which has low etch rate in the BHF solution and also heatresistance. The protection layer 144 can be formed on the glasssubstrate by virtually any standard means including a vapor depositiontechnique such as RF magnetron sputtering, Plasma-enhanced chemicalvapor deposition (PECVD), low-pressure chemical vapor deposition (LPCVD)to name but a few.

As shown in FIG. 2D, the fabrication process may include a step offabricating the film battery element 150 on the support substrate 142with the protection layer 144 interposed therebetween. The film batteryelement 150 may be fabricated on the support substrate by using anyconventional process. For example, the film battery element 150 can befabricated by a sequence of vapor deposition processes.

The exemplary process of fabricating the film battery element 150 mayinclude (a) a step of depositing anode and cathode current collectors152,160 on the protection layer 144; (b) a step of depositing a cathode154 on the cathode current collector 152 under low temperature; (c) astep of annealing the cathode 154 at a predetermined annealingtemperature (e.g. in a range of 500-700 degrees Celsius) to obtain afully crystalline phase; (d) a step of depositing an electrolyte 156with fully covering the cathode 154; and (e) a step of depositing ananode 158 on the electrolyte 156 and the anode current collector 160. Inother embodiment, the process may include (f) a step of depositing thecathode 154 on the cathode current collector 152 under a predetermineddeposition temperature while heating the support substrate 142, insteadof the steps of (b) and (c).

As shown in FIG. 2C, the fabrication process may further include a stepof forming the insulator 162 over the film battery element 150 and theprotection layer 144 to obtain a battery layer 140 formed on the supportsubstrate 142 with the protection layer 144 interposed therebetween.

In a particular embodiment, the step of forming the insulator 162 mayinclude a sub-step of depositing an insulation material over the filmbattery element 150; and a subsequent sub-step of flattening of theinsulation material to obtain a flat top surface 162 a by squeezing theinsulation material, fly-cutting the insulation material, or chemicallyand mechanically polishing the insulation material. Alternatively, thesub-step of flattening can be done based on spin on glass techniquewhere the support substrate 142 retaining insulation material depositedthereon are spun at high speeds to distribute the isolation materialuniformly across a top surface of the protection layer 144.

By repeating the steps described in the series of FIGS. 2C-2E apredetermined number of times, the desired number of the battery layers140 formed on respective support substrate 142 can be preparedseparately. Note that the steps described in the series of FIGS. 2C-2Emay be repeated in parallel or in series, and performed after or beforethe steps described in the series of FIGS. 2A-2B.

As shown in FIG. 3A, the fabrication process may include a step ofplacing the battery layer 140A with the support substrate 142A onto thebase substrate 102 with the bottom of the support substrate 142A facingup. In the described embodiment, since the base substrate 102 isprovided with the base battery layer 110 formed thereon, the batterylayer 140 is disposed on the insulator 132 of the base battery layer 110in an upside down manner such that the insulator 162 is on the side ofthe base substrate 102 and the protection layer 144 (and the supportsubstrate 142A), where the film battery element 150A is fabricated on,is on a side opposite to the base substrate side.

As shown in FIG. 3B, the fabrication process may include a step ofremoving the support substrate 142A from the battery layer 140A byetching while protecting the film battery element 150A by the protectionlayer 144A. The etching may be chemical etching. In the describedembodiment, the support substrate 142 may be completely eliminated fromthe battery layer 140 by wet-etching the support substrate 142 untilreaching the protection layer 144 as illustrated in FIG. 3B, whileleaving its underlying structure untouched. When the support substrate142 is made of glass material and the base substrate 102 is made ofsilicon material, the wet-etching using BHF solution can be employedsince it has high selectivity for the silicon dioxide SiO₂ over thesilicon. The protection layer 144 works as an etch stopper against BHFwet-etching.

If the base substrate 102 is made of a material having resistanceagainst BHF such as silicon, the backside of base substrate 102 is notrequired to be protected during the wet-etching. Thus, a special tool ormaterial for protecting the base substrate 102 can be made unnecessary.However, in other embodiments, a material not having resistance againstBHF is not excluded as a material of the base substrate 102, as long asthe backside of the base substrate 102 can be protected by any knowntool such as wafer chucks or chemically resistant material such assilicon nitride, which allows for back-side protection duringwet-etching.

Note that the support substrate 142 is illustrated as being fullyeliminated from the battery layer 140 in FIG. 3B. However, analternative embodiment where the support substrate 142 is removed fromthe battery layer 140A in part by etching may also be contemplated.

As shown in FIG. 3C, the fabrication process may include a step ofrepeatedly stacking the additional battery layer (e.g. 140B) until thedesired number of the battery layers 140 is stacked. The step ofrepeatedly stacking the additional battery layer 140 may includealternately performing a sub-step of stacking the additional batterylayer 140 with other support substrate 142 and a sub-step of removingthe support substrate 142 from the additional battery layer 140. Foreach repeating cycle, the additional battery layer 140 with the supportsubstrate 142 is stacked with the bottom of the support substrate 142facing up. Then, the support substrate 142 is removed from theadditional battery layer 140 at least in part by etching in the same wayas described with reference to FIG. 3B.

In a particular embodiment, after the desired number of the batterylayers 140 are stacked, the insulators 132, 162A, 162B, which may bepartly cured after each time stacking the battery layer 140, are fullycured by making the resin of the insulator 132, 162A, 162B undergo thecuring temperature. By fully curing the insulator 132, 162A, 162B, eachof upper and lower layers in the stacked battery layers 110, 140A, 140Bare rigidly fixed to each other.

As shown in FIG. 4A, the fabrication process may include a step offorming via holes 170 a, 170 b into the stacked battery layers 110,140A, 140B. The via holes 170 a, 170 b may extend through at least onelayer to its underlying layer, when the support substrates 142 down tothe layer have been eliminated by the etching. In FIG. 4A, the supportsubstrates 142B, 142A down to the battery layer 140A have beeneliminated by the etching and the via holes 170 a, 170 b extends throughtwo battery layers 140B, 140A to its underlying layer 110. The via holes170 a, 170 may be formed in the stacked battery layers perpendicular toor obliquely to the base substrate 102.

If a laser-processable insulator material is used for the insulator 132,162A, 162B, the via holes 170 a, 170 b can be formed by directlydrilling both of the insulators 162B, 162A, 132 and the protection layer144B, 144A in the stacked battery layers by laser processing whileleaving the current collector 122, 130, 152, 160. The hole may have adimension of several tens micrometers (e.g., 50 um diameter/width).

As shown in FIG. 4B, the fabrication process may include a step offilling a conductive material in the via holes 170 a, 170 b to form thevias 172, 174 as the conductive paths. The filling of the conductivematerial can be performed by virtually any standard means such as solderpaste filling. In the described embodiment, each via 172 (or 174) iselectrically connected to the respective current collectors 122, 152A,152B (or 130, 160A, 160B) in the stacked battery layers. In alternativeembodiment, the fabrication process may include a step of depositing aconductive material on the inner surface of the via holes 170 a, 170 binstead of filling with the conductive material.

By performing the steps described in a series of FIGS. 4A-4B, theconductive paths, each of which is connected to the respective currentcollectors, can be formed within the stacked battery layers 110, 140.The process for fabricating the conductive path will be described laterin more detail.

As shown in FIG. 4C, the fabrication process may include a step ofbuilding the wiring layer 180 on the top of the battery layers 110,140A, 140B. The wiring layer 180 may have a conductive element thatconnects the vias 172, 174 with external terminals, which is used toconnect to an external device, such as a CPU or memory. A resin may beformed over the conductive element as an insulator.

Although the aforementioned description has been focused on a singlestacked battery structure 100, the fabrication process can be conductedon not only the chip or package level but also wafer or panel level. Ina particular embodiment, the base substrate 102 and the supportsubstrate 142 may have a wafer or panel form, and the base substrate 102and the support substrate 142 may include a plurality of the filmbattery elements 120, 150 formed thereon. After bonding the plurality ofthe battery layers 110, 140, which may be in a form of a wafer or panel,may be diced into a plurality of chips, each of which has a structureidentical to the stacked battery structure 100 shown in FIG. 1.

According to the exemplary embodiment shown in FIGS. 2A-2E, FIGS. 3A-3Cand FIGS. 4A-4C, since each battery layer 110, 140 prepared for stackinghas the film battery element 120, 150 that is already fabricated thereonseparately, other components of the stacked battery structure 100 wouldnot be damaged due to the heating process for cathode 124, 154, incontrast to sequential stacking that fabricates multiple layers ofelectrochemical cells sequentially, in which previously formed othercomponents such as an anode for a lower layer should withstand theheating process for the cathode to be formed later for an upper layer.In other words, the material of the cathode 124, 154 can be transformedinto a crystalline phase without damaging the other components.

Since the most probable thermal process after the stacking may be curingof the insulator 132, 162 and the wiring layer 180, the other componentswould not be damaged throughout the fabrication process as long as thecomponents of the stacked battery structure 100 can withstand the curingtemperature.

With reference to a series of FIG. 5 and FIGS. 6A-6E, a process forfabricating a via having a stepped shape structure according to theexemplary embodiment of the present invention will be described.

FIG. 5 shows a schematic of connected current collectors 122, 152 by thevia 172 in the stacked battery structure 100. In FIG. 5, there are across-sectional view 200 of the stacked battery structure 100, top views210, 220, 230 of three battery layers 110, 140A, 140B at a portionaround the cathode current collector 122, 152A, 152B (as indicated by adashed circle P in FIG. 5) before stacking. A relation between thecross-sectional view 200 and the top views 210, 220, 230 is depicted byarrows and labels in FIG. 5. The cross-sectional view 200 corresponds toa cross-section indicated by the “X” in the top views 210, 220, 230 ofFIG. 5. Note that the outlines of the current collectors 152, 160 thatdo not appear in the cross section of the cross-sectional view 200 areindicated by dashed lines in FIG. 5.

In FIG. 5, there are further top views 240, 250, 260 of the stackedbattery layers just after the stacking step, just after the via holeforming step and just after the filling step, respectively. FIGS. 6A-6Eillustrates a process for fabricating the via 172 with the stepped shapestructure. The cross-sectional views shown in FIGS. 6A-6E correspond toan enlarged view of a portion indicated by a dashed circle P along witha cross-sections indicated by the “V” in the FIG. 5.

As shown in the top view 210 for the first layer (i.e., the base batterylayer 110), the base substrate 102, the cathode current collector 122,which is indicated by dashed rectangle in the top view 210, and theinsulator 132 are layered. As shown in the top views 220, 230, theinsulator 162, the cathode current collector 152, which is alsoindicated by dashed rectangles in the top view 220, 230, and theprotection layer 144 are layered for each of the second and third layers(i.e., the battery layer 140A, 140B). Note that locations of the cathodecurrent collectors 122, 152A, 152B (possibly together with the entirestructure of the film battery element 120, 150A, 150B) are shifted alongwith a direction in a horizontal plane of the base substrate 102.

The top view 240 in FIG. 5 shows the top surface of the stacked batterylayers 110, 140A, 140B just after the stacking steps of the desirednumber of the battery layers 110, 140. FIG. 6A depicts a cross-sectionalview of the stacked battery layers 110, 140A, 140B just after thestacking steps. As shown in the top view 240 of FIG. 5, the top surfaceof the protection layer 144B of the third battery layer 140B can be seenjust after the stacking steps.

The top view 250 in FIG. 5 shows the top surface of the stacked batterylayers 110, 140A just after the via hole forming step. FIG. 6B depicts across-sectional view of the stacked battery layers 110, 140A, 140B justafter the via hole forming step. By drilling the protection layers 144B,144A and the insulators 162B, 162A, 132 from the top to bottom, the viahole 170 a is fabricated through the stacked battery layers 110, 140A,140B. Note that the current collector 152B, 152A, 122 may work as astopper for laser drilling, accordingly, the current collector 152B,152A, 122 would leave on the insulator 162B, 162A, 102 with theirunderlying structures untouched after the course of the laserprocessing.

As shown in FIG. 6B, the via hole 170 a may have at least one respectivehorizontal dimension enlarged from bottom to top in the stacked batterylayers 110, 140A, 140B and each section may overlap each other in ahorizontal plane of the base substrate 102. As shown in the top view 250of FIG. 5, after the via hole forming step, surfaces of all cathodecurrent collectors 122, 152A, 152B can be seen through the via hole 170a when viewed from normal direction with respect to the base substrate102.

FIGS. 6C-6E show the process of via fabrication after making the throughhole 170 a with cross-sectional views of the structure. FIG. 6F showsthe alternative process of via fabrication after making the through hole170 a with a cross-sectional view of the structure.

As shown in FIG. 6C, an inner surface of the via hole 170 a may becoated with an insulation material (e.g., polymer) 176. The coating ofthe insulation material can be performed by any standard means such asvapor deposition polymerization.

As shown in FIG. 6D, then, portions of the insulation material 176 thatare deposited on the cathode current collectors 122, 152A, 154B may beetched back by standard anisotropic etching so as to expose the surfacesof the cathode current collectors 122, 152A, 152B. At this point, thevia hole 170 a may have plural sections, each of which has a terraceexposing the cathode current collector (e.g., the cathode currentcollectors 152A, 152B) or an inner bottom surface exposing the cathodecurrent collector (e.g., the cathode current collector 122).

As shown in FIG. 6E, the conductive material are filled into the hole170 a to form the via 172. The top view 260 in FIG. 5 shows the topsurface of the stacked battery layers 110, 140A just after the fillingstep. As shown in the top view 260, after the filling step, the top endof the via 172 that exposes at the top surface of the protection layer144B of the third battery layer 140B can be seen when viewed from thenormal direction with respect to the base substrate 102 while allcathode current collectors 122, 152A, 152B are covered by the conductivematerial. Alternatively, the conductive material may be deposited on theinner surface of the via hole 170 a to form the via 172 as shown in FIG.6F.

Note that the step of coating the inner surface of the via hole 170 aand a step of etching back the portions of the insulation material 176may be omitted if there is no conductive material that exposes at theinner surface of the via hole 170 a other than current collectors 152,122. In a particular embodiment where the protection layer 144 is madeof insulation material such as the silicon nitride, and the supportsubstrates 142 are completely eliminated by etching or the supportsubstrates 142 is made of insulation material such as glass when thesupport substrates 142 is still present in part, the step of coating andthe step of etching back can be omitted.

Such stepped shape structure shown in FIGS. 6E and 6F would enable thestacked battery structure 100 to have reliable contacts between the via172 and the current collectors 122, 152A, 152B in the stacked batterystructure 100.

Hereinafter, with reference to FIGS. 7A and 7B, variations of stackedbattery structure according to one or more exemplary embodiments of thepresent invention will be described.

In the aforementioned embodiment, there are three battery layers 110,140A, 140B in the stacked battery structure 100 for a purpose ofillustration. However, the number of the battery layers 110, 140 in thestacked battery structure 100 may not be limited to the specificembodiment described hereinabove. In one or more other embodiments, twoor more than three battery layers 110, 140 may be stacked to form thestacked battery structure 100.

FIG. 7A shows a stacked battery structure 200 having an upward basebattery layer 210 and eight downward battery layers 240A-240H, ninebattery layers in total stacked on the base substrate 202, each of whichhas a film battery element 220, 250.

Furthermore, in the aforementioned embodiment, the downward batterylayers 140 are described as being formed on the base substrate 102 withthe base battery layer 110 interposed therebetween. However, in otherembodiments, the downward battery layers 140 may be formed directly onthe base substrate 102 without the base battery layer 110 interposedtherebetween.

FIG. 7B shows a stacked battery structure 300 having nine downwardbattery layers 340A-340I stacked on the base substrate 302, each ofwhich has a film battery element 350.

It is necessary to perform merely eight times stacking steps tofabricate the stacked battery structure 200 while it is necessary toperform nine times to fabricate the stacked battery structure 300, thusthe stacked battery structure 200 with the base battery layer 210 ismore advantageous than the stacked battery structure 300.

Hereinafter, referring to FIGS. 8A and 8B, schematics of electronicdevice including a stacked battery structure 100 according to one ormore exemplary embodiments of the present invention will be described.The electronic device can be used for an IoT device.

FIG. 8A depicts a schematic of a system-on-package configuration for anelectronic device that includes the stacked battery structure 100. Asshown in FIG. 8A, the stacked battery structure 100 may be mounted on awiring substrate 190 on which one or more external electronic components192A, 192B such as a processor, memory, sensor are mounted.

FIG. 8B depicts a schematic of system-on-battery configuration for anelectronic device that includes the stacked battery structure 100. Asshown in FIG. 8B, the stacked battery structure 100 works as aninterposer or substrate onto which one or more electronic components172A, 172B are mounted. In this embodiment, the stacked batterystructure 100 has the wiring layer 180 on the top surface of the stackedbattery layers 110, 140A, 140B for connecting the stacked batterystructure 100 with one or more electronic components mounted on thestacked battery structure 100. The system-on-battery configuration maybe advantageous for further miniaturization.

Since a power source of the electronic device has a small footprint, anoverall size of the electronic device can be miniaturized.

According to one or more embodiments of the present invention, the totalthickness of the battery structure can be thinned while maintaining itscapacity, or alternatively, the capacity of the battery structure can beenlarged while keeping total thickness of the battery structure.

Referring to FIGS. 9A and 9B, a comparison between stacked batterystructures with and without applying the novel support substrate removalprocess according to the exemplary embodiment of the present inventionis described.

FIG. 9A and FIG. 9B show stacked battery structures having three batterylayers without and with an intermediate substrate. The stacked batterystructure shown in FIG. 9A has one base battery layer 110 and twobattery layers 140A, 140B, in which the support substrates 142A, 142Bused to support the film battery element 150A, 150B during thefabrication process have been completely eliminated by the novel supportsubstrate removal process. On the other hand, the stacked batterystructure 500 shown in FIG. 9B also has one base battery layer 510 andtwo battery layers 540A, 540B, in which the substrates 542A, 542B wherethe film battery element 550A, 550B is formed on is still present in thefinal structure 500.

As described above, even though the substrates 542A, 542B can be thinneddown to 75 to 50 um by a standard back grinding process, the thicknessof the substrates 542A, 542B is still several times thicker than thethickness of the film battery element 520, 550A, 550B that may be lessthan or equal to about ten micrometers (˜10 um).

As shown in FIG. 9B, there are alternating insulators 562 and substrates542 in the stacked battery structure 500. Thus, the insulator 562 needsto be removed before stacking, which may uses a pre-patterning processby photolithography to make a hole in the insulator 562. Also,anisotropic dry etching process is needed to drill the substrate 542after stacking, which may be silicon. Both of the pre-patterning processand the anisotropic dry etching process are expensive processes. Thus,the cost of drilling the via hole increases.

In contrast to the battery structure with the intermediate substrate 542shown in FIG. 9B, the stacked battery structure 100 according to the oneor more embodiments of the present invention, can have thinner totalthickness while maintaining its capacity since the support substrate 142which the film battery element 150 is formed on can be thinned, orpreferably eliminated while protecting the film battery element 150 bythe protection layer 144. In other words, the stacked battery structurecan have a large capacity while keeping total thickness of the batterystructure. Since the thickness to be increased by stacking one unit ofthe battery layer is small, it is possible to increase the number ofbattery layers stacked within a certain thickness and certain volume.Thus, it can be said it is volume efficient.

In the aforementioned embodiments, stacked structures having multiplethin film battery elements have been described. However, one or moreembodiments according to the present invention are not limited to thestacked structures having multiple thin film battery elements, and arealso directed to a method for fabricating a stacked structure, in whichhighly integrated device structure having a multiple devices, that isother than the battery can be achieved in a novel manner.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising”, when used in this specification, specify thepresence of stated features, steps, layers, elements, and/or components,but do not preclude the presence or addition of one or more otherfeatures, steps, layers, elements, components and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below, if any, areintended to include any structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of one or more aspects of the present inventionhas been presented for purposes of illustration and description, but isnot intended to be exhaustive or limited to the invention in the formdisclosed.

Many modifications and variations will be apparent to those of ordinaryskill in the art without departing from the scope and spirit of thedescribed embodiments. The terminology used herein was chosen to bestexplain the principles of the embodiments, the practical application ortechnical improvement over technologies found in the marketplace, or toenable others of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A method for fabricating a stacked batterystructure, the method comprising: preparing a base substrate; preparinga battery layer formed on a support substrate, the battery layerincluding a protection layer formed on the support substrate, a filmbattery element formed on the protection layer and an insulator coveringthe film battery element; placing the battery layer onto the basesubstrate with the bottom of the support substrate facing up; andremoving the support substrate from the battery layer at least in partby etching while protecting the film battery element by the protectionlayer.
 2. The method of claim 1, wherein the method further comprises,until a desired number of the battery layers is stacked, alternatelyrepeating: stacking an additional battery layer formed on one othersupport substrate with the bottom of the other support substrate facingup, the additional battery layer including a protection layer, a filmbattery element and an insulator; and removing the other supportsubstrate from the additional battery layer at least in part by etching.3. The method of claim 2, wherein the film battery element in eachbattery layer includes current collectors and a battery cell in contactwith the current collectors, the method further comprising: forming avia hole in the battery layers stacked on the base substrate to extendthrough at least one layer to a layer under the at least one layer,wherein the support substrates down to the layer have been eliminated bythe etching; and filling a conductive material in the via hole ordepositing a conductive material on an inner surface of the via hole toform a conductive path electrically connected to at least one currentcollector in the battery layers.
 4. The method of claim 3, whereinforming the via hole comprises: drilling at least one protection layerand at least one insulator in the battery layers by laser processingwhile leaving the current collector.
 5. The method of claim 4, whereinthe via hole has plural sections and the plural sections have at leastone horizontal dimension enlarged from bottom to top in the batterylayers and overlap each other in a horizontal plane with respect to thebase substrate, the conductive path has contacts with plural currentcollectors in different battery layers, each contact being obtained at asurface of each of the plural current collectors.
 6. The method of claim3, wherein the method further comprises: building a wiring layer on thetop of the battery layers, the wiring layer including a conductivepattern connecting the conductive path with an external terminal.
 7. Themethod of claim 1, wherein removing the support substrate comprises:wet-etching the support substrate until reaching the protection layer.8. The method of claim 7, wherein the support substrate is made of glassmaterial, the wet-etching includes etching using buffered hydrofluoricacid solution, the protection layer works as an etch stopper against thebuffered hydrofluoric acid solution and the base substrate is made of amaterial having resistance against the buffered hydrofluoric acidsolution.
 9. The method of claim 1, wherein the base substrate isprovided with a base battery layer formed thereon, the base batterylayer including a film battery element formed on the base substrate andan insulator covering the film battery element formed on the basesubstrate, the battery layer being placed onto the insulator of the basebattery layer in placing the battery layer onto the base substrate. 10.A method for fabricating a stacked structure, the method comprising:preparing a base substrate; preparing a device element layer formed on asupport substrate, the device element layer including a protection layerformed on the support substrate, a device element formed on theprotection layer and an adhesive material covering the device element;placing the device element layer onto the base substrate with the bottomof the support substrate facing up; and etching the support substratefrom the bottom of the support substrate until reaching the protectionlayer of the device element layer.
 11. The method of claim 10, whereinthe method further comprises, until a desired number of the deviceelement layers is stacked, alternately repeating: stacking an additionaldevice element layer formed on other support substrate with the bottomof other support substrate facing up; and removing the other supportsubstrate from the additional device element layer by etching.